When using a particular service, give appropriate size for your services like RAM & CPU size of your instance, instance types, etc. need to select the service capacity according to your business needs. You can easily enlarge your settings whenever you want. If you want your application in few times, you can also have the option to choose reserved instances, rds.
When you're using a AWS service(primary), it may require other AWS services also. So when you don't require primary AWS services, you need to remove other services also. You need to monitor your AWS services when auto scaling enabled for your AWS service.
Create alerts for your AWS services, how much you're going to use that service and how long? Creating alerts and dashboard of AWS services will give you insights of your application.
Using AWS Cost Explorer, we can analyze your costs and usage, also providing reports. Using the reports, we can easily identify cost and usage, manage your application according to your needs.
After creating AWS services, you need to keep an eye on all used AWS services. You can monitor all your AWS services every day.